Climate change likely to reduce orchid bee abundance even in climatic suitable sites.

Studies have tested whether model predictions based on species' occurrence can predict the spatial pattern of population abundance. The relationship between predicted environmental suitability and population abundance varies in shape, strength and predictive power. However, little attention has been paid to the congruence in predictions of different models fed with occurrence or abundance data, in particular when comparing metrics of climate change impact. Here, we used the ecological niche modeling fit with presence-absence and abundance data of orchid bees to predict the effect of climate change on species and assembly level distribution patterns. In addition, we assessed whether predictions of presence-absence models can be used as a proxy to abundance patterns. We obtained georeferenced abundance data of orchid bees (Hymenoptera: Apidae: Euglossina) in the Brazilian Atlantic Forest. Sampling method consisted in attracting male orchid bees to baits of at least five different aromatic compounds and collecting the individuals with entomological nets or bait traps. We limited abundance data to those obtained by similar standard sampling protocol to avoid bias in abundance estimation. We used boosted regression trees to model ecological niches and project them into six climate models and two Representative Concentration Pathways. We found that models based on species occurrences worked as a proxy for changes in population abundance when the output of the models were continuous; results were very different when outputs were discretized to binary predictions. We found an overall trend of diminishing abundance in the future, but a clear retention of climatically suitable sites too. Furthermore, geographic distance to gained climatic suitable areas can be very short, although it embraces great variation. Changes in species richness and turnover would be concentrated in western and southern Atlantic Forest. Our findings offer support to the ongoing debate of suitability-abundance models and can be used to support spatial conservation prioritization schemes and species triage in Atlantic Forest.

Current and historical climate signatures to deconstructed tree species richness pattern in South America / Efeitos dos climas atual e histórico no padrão desconstruído de riqueza de espécies arbóreas na região Neotropical

The purpose of this study was to investigate the importance of present and historical climate as determinants of current species richness pattern of forestry trees in South America. The study predicted the distribution of 217 tree species using Maxent models, and calculated the potential species richness pattern, which was further deconstructed based on range sizes and modeled against current and historical climates predictors using Geographically Weighted Regressions (GWR) analyses. The current climate explains more of the wide-ranging species richness patterns than that of the narrow-ranging species, while the historical climate explained an equally small amount of variance for both narrow-and-wide ranging tree species richness patterns. The richness deconstruction based on range size revealed that the influences of current and historical climate hypotheses underlying patterns in South American tree species richness differ from those found in the Northern Hemisphere. Notably, the historical climate appears to be an important determinant of richness only in regions with marked climate changes and proved Pleistocenic refuges, while the current climate predicts the species richness across those Neotropical regions, with non-evident refuges in the Last Glacial Maximum. Thus, this study's analyses show that these climate hypotheses are complementary to explain the South American tree species richness.

O objetivo deste estudo foi testar qual dos climas, atual ou histórico, é o principal preditor do padrão atual de riqueza de espécies arbóreas de interesse comercial. Nós modelamos a distribuição de 217 espécies usando Maxent e usamos esses mapas preditivos para obter o padrão de riqueza de espécies. A riqueza foi desconstruída em relação ao tamanho da distribuição geográfica das espécies e modelada contra os climas atual e histórico utilizando Regressões Geograficamente Ponderadas. O clima atual explicou melhor o padrão de riqueza das espécies com ampla distribuição geográfica do que de espécies com distribuição restrita, enquanto o clima histórico explicou a mesma variância na riqueza dos dois grupos de espécies. Nossas análises com plantas sul americanas mostram diferentes relações da riqueza de espécies ampla e restritamente distribuídas com os climas atual e histórico, quando comparado aos resultados encontrados no hemisfério norte. O clima histórico se mostra como importante preditor da riqueza somente em regiões com mudanças climáticas acentuadas e onde ocorreram refúgios Pleistocênicos, enquanto o clima atual é o melhor da riqueza nas regiões Neotropicais sem evidências de refúgios durante o máximo da ultima glaciação. Dessa maneira, nossos resultados indicam que essas hipóteses são complementares para explicar a riqueza predita de espécies arbóreas da América do Sul.